Channel aware sparse transmission for ultra low-latency communications in TDD systems

TL;DR

This paper introduces CAST, a novel channel-aware sparse transmission scheme for TDD systems that significantly reduces access latency in URLLC scenarios by leveraging compressed sensing techniques.

Contribution

The paper proposes CAST, a new low-latency access method for TDD systems that encodes grant signals as sparse vectors and utilizes compressed sensing for decoding.

Findings

CAST reduces access latency compared to LTE-TDD and 5G NR-TDD.

The scheme effectively supports URLLC requirements.

Numerical evaluations confirm performance improvements.

Abstract

Major goal of ultra reliable and low latency communication (URLLC) is to reduce the latency down to a millisecond (ms) level while ensuring reliability of the transmission. Since the current uplink transmission scheme requires a complicated handshaking procedure to initiate the transmission, to meet this stringent latency requirement is a challenge in wireless system design. In particular, in the time division duplexing (TDD) systems, supporting the URLLC is difficult since the mobile device has to wait until the transmit direction is switched to the uplink. In this paper, we propose a new approach to support a low latency access in TDD systems, called channel aware sparse transmission (CAST). Key idea of the proposed scheme is to encode a grant signal in a form of sparse vector. This together with the fact that the sensing mechanism preserves the energy of the sparse vector allows us to use the compressed sensing (CS) technique in CAST decoding. From the performance analysis and numerical evaluations, we demonstrate that the proposed CAST scheme achieves a significant reduction in access latency over the 4G LTE-TDD and 5G NR-TDD systems.